Techniques for language independent wake-up word detection

ABSTRACT

A user device configured to perform wake-up word detection in a target language. The user device comprises at least one microphone (430) configured to obtain acoustic information from the environment of the user device, at least one computer readable medium (435) storing an acoustic model (150) trained on a corpus of training data (105) in a source language different than the target language, and storing a first sequence of speech units obtained by providing acoustic features (110) derived from audio comprising the user speaking a wake-up word in the target language to the acoustic model (150), and at least one processor (415,425) coupled to the at least one computer readable medium (435) and programmed to perform receiving, from the at least one microphone (430), acoustic input from the user speaking in the target language while the user device is operating in a low-power mode, applying acoustic features derived from the acoustic input to the acoustic model (150) to obtain a second sequence of speech units corresponding to the acoustic input, determining if the user spoke the wake-up word at least in part by comparing the first sequence of speech units to the second sequence of speech units, and exiting the low-power mode if it is determined that the user spoke the wake-up word.

RELATED APPLICATION

This Application is a national stage filing under 35 U.S.C. 371 ofInternational Patent Application Serial No. PCT/CN2016/105343, filedNov. 10, 2016, and titled “TECHNIQUES FOR LANGUAGE INDEPENDENT WAKE-UPWORD DETECTION.” The entire contents of this application areincorporated herein by reference in their entirety.

BACKGROUND

A system may be speech enabled, allowing users to interact with thesystem via speech, for example, by allowing users to speak commands tocontrol the system. Engaging a speech-enabled system often requiresusers to signal to the speech-enabled system that the user intends tointeract with the system by speaking. For example, a speech-enabledsystem may be configured to begin recognizing speech after a manualtrigger, such as a button push (e.g., a button of a physical deviceand/or a button within a user interface of a speech recognition softwareapplication), launch of an application, or other manual interaction withthe system, is provided to wake-up a device or to alert the system thatspeech following the manual trigger is directed to the system. However,manual triggers complicate the interaction with the speech-enabledsystem and, in some cases, may be inconvenient or impossible to use(e.g., when the user's hands are otherwise occupied, such as whenoperating a vehicle, or when the user is too remote from the system tomanually engage with the system or an interface thereof).

When a mobile device is operating in a low power mode (e.g., in a sleep,hibernate or idle mode), the actions required to engage the voiceresponse system typically become even more extensive. In particular, theuser need first wake-up the mobile device itself before the voiceresponse system can be engaged using manual action or an explicit voicetrigger. For example, a user may have to press a button to turn-on thedisplay and/or enable one or more processors, may have to manipulate oneor more controls to ready the mobile device for use, and/or may have toinput a passcode if the mobile device has been inactive for a certainperiod of time. To address the inconvenience (and often inapplicability)of manual triggers, some speech-enabled systems allow for voice triggersto be spoken to begin engaging with the system, thus eliminating atleast some (if not all) manual actions and facilitating generallyhands-free access to the speech-enabled system. A voice trigger maycomprise a designated word or phrase (e.g., “Hello Dragon”) that isspoken by the user to indicate to the speech-enabled system that theuser intends to interact with the system (e.g., to issue one or morecommands to the system).

A voice trigger is also referred to herein as a “wake-up word” or “WuW.”After a wake-up word has been detected, the system begins recognizingsubsequent speech spoken by the user. In most cases, unless and untilthe system detects the wake-up word, the system will assume thatacoustic input received from the environment is not directed to orintended for the system and will not process the acoustic input further.If a device (e.g., a mobile device such as a smart phone) is operatingin a low-power mode, the device will remain inactive until a wake-upword is detected by the device.

SUMMARY

Some embodiments include a method of enabling wake-up word detection ina target language on a user device is provided. The method comprisesreceiving acoustic input of a user speaking a wake-up word in the targetlanguage, providing acoustic features derived from the acoustic input toan acoustic model stored on the user device to obtain a sequence ofspeech units corresponding to the wake-up word spoken by the user in thetarget language, the acoustic model trained on a corpus of training datain a source language different than the target language, and storing thesequence of speech units on the user device for use in subsequentwake-up word detection.

Some embodiments include user device configured to enable wake-up worddetection in a target language, the user device comprising at least onemicrophone configured to obtain acoustic information from theenvironment of the user device, at least one computer readable mediumstoring an acoustic model trained on a corpus of training data in asource language different than the target language, and at least oneprocessor coupled to the at least one computer readable medium andprogrammed to perform receiving, from the at least one microphone,acoustic input from the user speaking a wake-up word in the targetlanguage, providing acoustic features derived from the acoustic input tothe acoustic model to obtain a sequence of speech units corresponding tothe wake-up word spoken by the user in the target language, and storingthe sequence of speech units on the user device for use in subsequentwake-up word detection.

Some embodiments include a user device configured to perform wake-upword detection in a target language. The user device comprises at leastone microphone configured to obtain acoustic information from theenvironment of the user device, at least one computer readable mediumstoring an acoustic model trained on a corpus of training data in asource language different than the target language, and storing a firstsequence of speech units obtained by providing acoustic features derivedfrom audio comprising the user speaking a wake-up word in the targetlanguage to the acoustic model, and at least one processor coupled tothe at least one computer readable medium and programmed to performreceiving, from the at least one microphone, acoustic input from theuser speaking in the target language while the user device is operatingin a low-power mode, applying acoustic features derived from theacoustic input to the acoustic model to obtain a second sequence ofspeech units corresponding to the acoustic input, determining if theuser spoke the wake-up word at least in part by comparing the firstsequence of speech units to the second sequence of speech units, andexiting the low-power mode if it is determined that the user spoke thewake-up word.

Some embodiments include a method of performing wake-up word detectionon a user device, the method comprising, while the user device isoperating in a low-power mode, receiving acoustic input from a userspeaking in a target language, providing acoustic features derived fromthe acoustic input to an acoustic model stored on the user device toobtain a first sequence of speech units corresponding to the acousticinput, the acoustic model trained on a corpus of training data in asource language different than the target language, determining if theuser spoke the wake-up word at least in part by comparing the firstsequence of speech units to a second sequence of speech units stored onthe user device, the second sequence of speech units obtained byapplying acoustic features derived from audio comprising the userspeaking the wake-up word in the target language to the acoustic model,and exiting the low-power mode if it is determined that the user spokethe wake-up word.

BRIEF DESCRIPTION OF DRAWINGS

Various aspects and embodiments will be described with reference to thefollowing figures. The figures are not necessarily drawn to scale.

FIG. 1 illustrates an example of an acoustic model providing sequencedate from acoustic features derived from acoustic input;

FIG. 2 illustrates a method for enabling language independent wake-upword detection, in accordance with some embodiments;

FIG. 3 illustrates a method of performing wake-up word detection in auser's language, in accordance with some embodiments;

FIGS. 4A and 4B illustrate an exemplary mobile device on which languageindependent wake-up word detection can be enabled and performed, inaccordance with some embodiments; and

FIG. 5 illustrates an exemplary computer system on which techniquesdescribed herein may be performed.

DETAILED DESCRIPTION

As discussed above, wake-up word detection facilitates voice activationof a device (e.g., a mobile device operating in a low-power mode).However, wake-up word detection may not be available in the languagespoken by a given user. In particular, automatic speech recognitiongenerally involves processing a speech signal to extract relevantacoustic characteristics (e.g., Mel-frequency cepstral coefficients(MFCCs)) from the speech signal and applying the acousticcharacteristics to an acoustic model configured to provide hypothesesregarding the likely sequence of fundamental speech units (e.g., phones,phonemes, etc.) contained in the speech signal. Acoustic models aretypically trained using a relatively large corpus of training data to asto correctly identify the phonetic content of a spoken utterance. Forexample, acoustic training may be utilized to train one or more acousticmodels. Via training, an acoustic model “learns” acousticcharacteristics of the training data utilized so as to be able toaccurately identify sequences of speech units in speech data receivedwhen the trained ASR system is subsequently deployed. To achieveadequate training, relatively large amounts of training data in a givenlanguage are generally needed (e.g., hundreds or thousands of hours ofspeech data) to learn the characteristics and statistics of thecorresponding language.

A number of machine learning techniques have been used to implementacoustic models including, but not limited to, multi-layer neuralnetworks, hidden Markov models (HMMs), Gaussian mixture models (GMMs),etc. Larger speech units such as words or phrases are then determinedfrom the hypotheses regarding the sequence of fundamental speech unitsdetermined by the acoustic model. Typically, a language model trained tocapture the language statistics to provide the likelihood of particularword sequences is then used to hypothesize the most likely sequence ofwords represented by the sequence of speech units produced by theacoustic model. In this way, a speech input can be converted into thesequence of words contained in the speech signal, thus converting anaudio signal to its language content.

Modern systems frequently provide automatic speech recognition servicein the cloud. In particular, speech recognition services are frequentlyprovided by automatic speech recognition servers accessible via one ormore networks (e.g., via the Internet). Network connected devices (e.g.,personal computers, mobile devices such as laptops and smart phones,etc.) can thereby access speech recognition services to have the contentof speech input received by the network connected devices recognized viathe cloud. Often a speech recognition service will provide comprehensivespeech recognition services in numerous languages, for example, bytraining acoustic models and language models in various desiredlanguages. In this way, sophisticated automatic speech recognition innumerous languages can be performed using any device capable ofcommunicating over a network (e.g., capable of accessing the Internet)and configured to communicate with automatic speech recognitionservice(s). In the mobile context, a user may speak to the user's mobiledevice (e.g., a smart phone, personal digital assistant, wearabledevice, or any other mobile device) and the speech captured by themobile device can be transmitted over the network to be recognized by anautomatic speech recognition service provide via the cloud.

However, mobile devices are generally power-limited in that they arefrequently expected to operate for relatively extended periods of timeoff of battery power. To conserve power, mobile devices frequently entera low power mode (e.g., a sleep, idle or hibernate mode) after someduration of inactivity. A low power mode refers generally to any mode orstate that is entered to conserve power that conventionally requires oneor more wake-up actions to exit (e.g., to activate the mobile device).Mobile devices may have more than one low power mode and differentmobile devices may power down different components when entering a lowpower mode. However, mobile devices will typically have some variationof a low power mode that conventionally requires action to exit the lowpower mode and transition to an active mode.

Entering a low power mode may include turning off the display, shuttingdown one or more processors (e.g., disabling the clock tree associatedwith one or more processors) and/or deactivating components that wouldotherwise draw power if left operational. Automatically entering a lowpower mode after a designated interval of time may significantly extendthe period that a mobile device can operate on battery power beforerequiring a recharge. In view of the relative importance of conservingpower in a mobile device, many mobile devices default to a relativelyshort duration of inactivity before powering down and going to sleep,such that a mobile device may frequently be in a low power mode when auser wants to access functionality on the mobile device.

As such, when operating in low-power mode, a mobile device typicallywill not have access to automatic speech recognition services providedin the cloud because establishing a network connection to utilize cloudresources each time acoustic input is received by the mobile device(e.g., when a microphone detects acoustic activity) to assess whether awake-up word has been spoken could utilize significant enough processingpower to frustrate the efforts of powering down the mobile device to alow power mode in the first place. Therefore, wake-up word detectionusing network resources is generally not available and may not befeasible in many circumstances. As a result, wake-up word detection isgenerally performed using the limited resources available to the mobiledevice while operating in the low-power mode (e.g., a voice activitydetector, a phone loop component, a low-power processor to perform smallvocabulary recognition, etc). Thus, a suitably trained acoustic modelmay not be available on a mobile device for the range of languages forwhich wake-up word detection is sought, at least in part becauseacoustic models in numerous or even multiple languages are generally notavailable on the mobile device itself. As a consequence, wake-up worddetection may be unavailable for a wide range of speakers that wouldlike this feature to be available in their own spoken language.

The inventors have recognized that an acoustic model trained for a firstlanguage can be used to recognize the phonetic content of an utterancespoken in a second language different than the first language. As usedherein, an acoustic model trained for a first language or trained via afirst language refers to an acoustic model that is trained usingtraining data predominantly, substantially or exclusively in a firstlanguage. In this way, an acoustic model trained for a first languagecan be used to assist in performing wake-up word detection in anydesired language, regardless of whether a trained acoustic model isavailable to the mobile device for that desired language. Accordingly,language independent wake-up word detection may be performed using anyavailable and suitably trained acoustic model (e.g., an acoustic modelon a mobile device and/or available to a mobile device in a low-powermode).

According to some embodiments, a user speaks an enrollment utterancethat includes, or consists of, a desired wake-up word in a desiredlanguage (target language) that, for example, a trained acoustic modelmay not be available. For example, a mobile device for which wake-upword detection in the desired language is sought may not have storedthereon an acoustic model trained for the desired language and/or whilesuch an acoustic model may be available via the cloud, no such acousticmodel may be available when the mobile device is operating in alow-power mode. However, an acoustic model trained for a second language(source language) may be available (e.g., may be stored on a mobiledevice and/or accessible while the mobile device is operating in alow-power mode). Acoustic features derived from the enrollment utterancemay be applied as input to the available acoustic model to obtain asequence of speech units (e.g., phonemes, di-phones, tri-phones, HMIstates, or any other suitable sub-word speech unit) believed tocorrespond to the received acoustic features. The resulting sequence ofspeech units can then be stored as the pronunciation of the wake-up wordspoken by the user in the desired language (e.g., may be stored in auser dictionary as the pronunciation of the speaker of the desiredwake-up word). That is, the pronunciation may be stored and associatedwith the desired wake-up word for use in subsequent wake-up worddetection.

According to some embodiments, the enrollment utterance is used to adaptthe acoustic model to the speaker. In particular, speaker adaptation maybe applied to the acoustic model to obtain a speaker-adapted acousticmodel that can be used for the speaker to perform wake-up worddetection. For example, the enrollment utterance and the resultingsequence of speech units from the acoustic model may be used to adaptthe acoustic model to the user. In this manner, an acoustic model thathas been trained, for example, based on a large corpus of training datafor a source language can be used and adapted to perform wake-up worddetection of a desired target language. As such, language independentwake-up word detection may be implemented by performing the processdiscussed above and described in further detail below. According to someembodiments, one or more noise models may be added to the enrollmentutterance to improve the robustness of wake-up word detection in thepresence of noise and to facilitate speaker adaptation.

Following below are more detailed descriptions of various conceptsrelated to, and embodiments of, techniques of language independentwake-up word detection. It should be appreciated that various aspectsdescribed herein may be implemented in any of numerous ways. Examples ofspecific implementations are provided herein for illustrative purposesonly. In addition, the various aspects described in the embodimentsbelow may be used alone or in any combination, and are not limited tothe combinations explicitly described herein.

FIG. 1 illustrates an acoustic model 150 trained via training data 105,for example, a large corpus of speech data for a given language (e.g.,English). Acoustic model 150 is configured to receive, as an input,acoustic features 110 derived and/or extracted from speech data (e.g.,MFCCs or other desired acoustic features extracted from a desired numberof adjacent and/or overlapping frames of input speech data). Duringtraining, acoustic features 110 correspond to acoustic features derivedfrom training data 105 and, during deployment subsequent to training,features 110 correspond to acoustic features derived from speech data tobe recognized. Acoustic model 150 includes a plurality of configurableparameters whose values may be iteratively adjusted during training. Thenature of the plurality of parameters will depend on the type ofacoustic model being used (e.g., neural network, HMM, GMM, etc.).

Acoustic model 150 outputs sequence data 120 in response to receivedacoustic features 110 in a manner governed by a current set of valuesassigned to the respective plurality of configurable parameters.Sequence data 120 generally comprises a hypothesis for the sequence ofspeech units (e.g., phonemes, diphones, triphones or any other suitablesub-word speech unit) believed to correspond to the received acousticfeatures 110. During training, the outputted sequence data 120 may becompared to expected sequence data (also referred to herein as “groundtruth”) and, based on the comparison, the current set of values (or aportion of the current set of values) of the plurality of parameters areadjusted accordingly.

The expected sequence data may be obtained in a number of ways, forexample, by using an existing trained acoustic model known to giveresults of sufficient accuracy/quality and applying the training data tothe existing trained acoustic model, using stored sequence datapreviously obtained for the training data, expert generated sequencedata (if feasible), or some combination thereof. The process ofproducing sequence data, comparing the sequence data to expectedsequence data and updating values of the parameters of the acousticmodel is repeated using the available training data. After completion oftraining, the trained acoustic model has a set of values established forthe plurality of parameters that produces sequence data in accordancewith what the acoustic model “learned” from processing the trainingdata. When deployed to perform automatic speech recognition (ASR),acoustic features derived from a user's speech input is provided to thetrained acoustic model, which outputs sequence data corresponding to ahypothesis of the word sequence spoken by the user.

As discussed above, an acoustic model trained for the user's spokenlanguage may not be available to a mobile device to perform wake-up worddetection (e.g., an acoustic model trained on training data in theuser's language may not be resident on the mobile device for use in alow power mode). Accordingly, voice activation of the mobile device maybe unavailable to the user. The inventors have developed techniques thatutilize an acoustic model trained using training data in a sourcelanguage to facilitate wake-up word detection in a target language forwhich an acoustic model trained for the target language is notavailable, as discussed in further detail below. As such, any acousticmodel available to the mobile device in a low power mode can be used toperform wake-up word detection in the user's language, as discussed infurther detail below.

FIG. 2 illustrates a method of utilizing an acoustic model trained for asource language to perform wake-up word detection on speech data of atarget language, in accordance with some embodiments. As used herein,the source language refers to the predominant, primary or exclusivelanguage of the training data on which an acoustic model was trained,and the target language refers to a language different from the sourcelanguage for which wake-up word detection is sought. In act 210, anenrollment utterance is obtained from a user speaking in the targetlanguage. For example, the user may speak an enrollment utterance thatincludes a wake-up word spoken in the target language, or the enrollmentutterance may consist exclusively of the wake-up word. The user may beprompted to speak a wake-up word predetermined by the system in thetarget language, or the user may be able to speak a wake-up word of theuser's choosing. The latter case allows a user to customize wake-up wordinteraction with their device and/or allows the user to utilize awake-up word as a command, as discussed in further detail below.

In act 220, the speech data corresponding to the wake-up word containedin the enrollment utterance is provided to an acoustic model trained fora source language (e.g., a well-trained acoustic model that has beentrained on a large corpus of speech data in the source language). Inparticular, acoustic features may be derived from the enrollmentutterance and processed by the trained acoustic model to recognize asequence of speech units (e.g., a phoneme sequence) corresponding to thewake-up word spoken in the target language. In this manner, the acousticmodel trained via the source language is used to produce a phonemesequence that characterizes the sounds of the wake-up word spoken in thetarget language.

In act 230, the sequence of speech units resulting from processing thewake-up word spoken in the target language is stored (e.g., in adictionary on the user's mobile device) as the reference sequence ofspeech units characterizing the wake-up word. For example, the sequenceof speech units may comprise the source language phoneme sequence thatcharacterizes the wake-up word spoken in the target language. Thisreference sequence of speech units can then be used upon deployment todetect when the user has spoken the wake-up word in the target language(e.g., by comparing an input sequence of speech units obtained using theacoustic model on speech data spoke by the user to a mobile deviceoperating in a low-power mode with the reference sequence of speechunits), as discussed in further detail below.

In act 240, one or more types of noise are added to the enrollmentutterance to obtain noisy enrollment utterances to improve theperformance of wake-up word detection in corresponding acousticenvironments. In particular, when a user is seeking to voice activate amobile device, the user and the device may be in an acoustic environmentdifferent than during enrollment. Specifically, a user may performenrollment in a relatively noise free environment but may wish toperform voice activation while driving, walking or in other acousticenvironments having spurious acoustic noise. Accordingly, the inventorshave appreciated that by adding one or more types of noise, wake-up worddetection may be improved. In particular, noise present in commonenvironments in which a user may speak a wake-up may be added to theenrollment utterance to improve wake-up word detection when used inthose common environments. For example, car noise, street noise or anyother desired noise may be added to the enrollment utterance and appliedto the acoustic model to obtain respective phoneme sequencescorresponding to the noisy enrollment utterance. Thereafter, theenrollment utterance, the noisy enrollment utterances and thecorresponding respective phoneme sequences are used to adapt theacoustic model to the noise environments corresponding to the one ormore noise models added to the enrollment utterance (i.e., in act 250described in further detail below). The noise adapted acoustic modelsmay then be used thereafter to improve performance of wake-up worddetection in the corresponding noise environments. It should beappreciated that any desired type of noise in any combination may beused to corrupt the enrollment utterance to adapt the acoustic model tothe corresponding noise environment, as the aspects are not limited inthis respect. It should be further appreciated that, in someembodiments, act 240 may not be performed.

In act 250, the enrollment utterance (i.e., the audio signal comprisingthe wake-up word), noisy enrollment utterances (e.g., in embodiments inwhich act 240 is performed), and the output of the acoustic modelprocessing acoustic features of the enrollment utterance (e.g., thereference sequence of speech units corresponding to the wake-up word)are used to perform speaker adaptation on the acoustic model. There arenumerous techniques for adapting an acoustic model to a speaker usingspeech data from the user. The choice of a particular adaptationtechnique may be driven by the type of acoustic model being adapted. Forexample, certain adaptation techniques may be more appropriate for a GMMor an HMM-based acoustic model than for a neural network-based acousticmodel. Suitable adaptation techniques include, but are not limited to,maximum a posteriori (MAP) adaptation, maximum likelihood linearregression (MLLR) adaption, a linear input network (LIN) layer (e.g.,for a neural network-based acoustic model), vocal tract lengthnormalization (VTLN), cluster adaptation techniques, eigenvoicetechniques, etc. Any suitable speaker-dependent adaptation may beperformed to provide an adapted acoustic model for the particular user,as the aspects are not limited in this respect. The adapted acousticmodel can then be used to improve the performance of wake-up worddetection for the user in the target language, as discussed in furtherdetail below.

It should be appreciated that while adapting the acoustic model usingthe enrollment utterance and/or using one or more noise modelsfacilitates improved wake-up word detection, such techniques areoptional and need not be performed (e.g., performing acts 240 and/or 250is optional), as performing language independent wake-up word detectionis not limited in this respect. Additionally, one or more tasks may beassociated with the wake-up word enrolled by the user. For example, auser may want one or more tasks to be performed, in addition to, or inplace of, transitioning from a low power when a wake-up word isdetected. For example, a user may provide an enrollment utteranceincluding the wake-up word “What time is it?” spoken by the user in thetarget language and a task by which the mobile device responds with thetime (e.g., by displaying the time on the display or synthesizing avoice response) may be associated with the reference sequence obtainedby processing this wake-up word using the acoustic model trained via thesource language. Providing the temperature, or providing an audiblealert (e.g., a beep, a ring) or a tactile alert (e.g., a vibration) toassist a user in locating their mobile device are further examples oftasks that may be associated with a wake-up word. Any suitable task maybe associated with a wake-up word, as the aspects are not limited inthis respect. Furthermore, it should be appreciated that acts 210-230(and optionally act 240) may be repeated to obtain reference sequencesfor any number of wake-up words. According to some embodiments, method200 can be employed to provide wake-up words that transition the mobiledevice to a variety of different power modes, perform tasks withoutleaving the current low-power mode and/or a combination thereof. In thismanner, a command vocabulary in the user's language can be created thatcan be used to activate the mobile device and/or to perform varioustasks associated with the same or different wake-up words, allowing auser to customize the voice activation capabilities of the user'sdevice.

It should be appreciated that the techniques described herein are notdependent on any particular source or target language. As long as anacoustic model that has been trained via a first language is available,a device can be enabled to perform wake-up word detection in anylanguage desired by the user, thus language independent wake-up worddetection can be achieved. That is, the techniques described herein arenot limited for use with any particular source language, target languageor source and target language combination.

FIG. 3 illustrates a method of performing wake-up word detection in atarget language using an acoustic model trained on training data in asource language different than the target language. In particular, theacoustic model may be the acoustic model from which a reference sequenceof speech units were obtained corresponding to a wake-up word spoken bya user in a target language different from the source language (e.g., areference sequence of speech units obtained and stored by performingmethod 200 described in connection with FIG. 2 ). Wake-up word detectionmay be performed, for example, on a user's mobile device operating in alow-power mode wherein the mobile device has a local acoustic model thatcan be utilized without exiting the low-power mode (e.g., withoutactivating or waking up the mobile device).

In act 310, acoustic input is received from the user. For example, amobile device may receive acoustic input from the environment in whichit is located. In act 320, the acoustic input is processed by theacoustic model trained via the source language to obtain an inputsequence of speech units corresponding to the acoustic input. Forexample, acoustic features (e.g., MFCCs) may be derived from theacoustic input and provided as input to the acoustic model which, inturn, generates a sequence of speech units corresponding to the acousticinput (e.g., generates a sequence of phonemes corresponding to thesounds present in the acoustic input).

In act 330, the input sequence of speech units is compared to thereference sequence of speech units, for example, stored in a dictionaryon the user's mobile device. In particular, the reference sequence ofspeech units obtained using the acoustic model trained via the sourcelanguage to process the enrollment utterance including the wake-up wordspoken by the user in the target language may be used to assess whetherthe input sequence of speech units is a match (e.g., to assess thelikelihood that the input sequence of speech of units also correspondsto the user speaking a wake-up word). The input and reference sequencesmay be compared in any suitable way that results in an indication ofsimilarity between the input and reference sequences, provides anindication of the likelihood that the input sequence corresponds to theuser speaking a wake-up word in the target language and/or produces adecision as to whether the input sequence of speech units is believed tohave resulted from the user speaking a wake-up word. In act 340, if itis determined that there is a match between the input and referencessequences of speech units (i.e., if it is determined that the inputsequence of speech units corresponds to the speaker having spoken awake-up word), the process of transitioning from low-power mode isinitiated and/or one or more tasks associated with the wake-up word maybe performed. For example, when it is determined that the user hasspoken a wake-up word, the process of waking up the user's mobile devicemay be initiated (e.g., the mobile device may be activated to an extentindicated by the wake-up word, such as transitioning the mobile deviceto an active state). As a result, the mobile device may be transitionedto an active mode for further interaction with the user.

As another example, when it is determined that the user has spoken awake-up word, it may be determined whether any tasks have beenassociated with the wake-up word determined to have been spoken by theuser and, if so, initiation and/or performance of one or more associatedtasks may be performed. It may be the case that in some instances, atask associated with a wake-up word does not require the mobile deviceto transition from the low-power mode (e.g., a task wherein the phonebeeps, vibrates or otherwise emits acoustic, tactile or other output toalert the user to its location, a task that presents the time, date,temperature, etc.) In such instances, the mobile device may remain inthe low power mode and the one or more tasks are performed in the lowpower mode. In other instances, performance of the task may require themobile device to exit the low power mode. Under such circumstances,low-power mode may be exited followed by performance of task(s)associated with the detected wake-up word. It should be appreciated thatact 330 may be performed against multiple reference sequences of speechunits that have been stored corresponding to multiple valid wake-upwords for which a reference sequence has been obtained. In this manner,language independent wake-up word detection and/or voice activated taskscan be performed, facilitating voice activation and/or control of amobile device in any language spoken by the user.

FIGS. 4A and 4B illustrate a mobile device that can be configured toperform language independent wake-up word detection for voice activationand/or control in any desired language. Mobile device 400 is illustratedas having a number of components characteristic of a “smart phone,” butit should be appreciated that mobile device 400 may be any generallyportable device capable of wireless communications (and/or wiredcommunications) and which includes an input capable of receivingacoustic input (e.g., one or more microphones). Mobile device 400includes one or more transducers 430 for converting acoustic energy toelectrical energy and vice versa. For example, transducers 430 mayinclude one or more speakers and/or one or more microphones arranged onthe mobile device to allow input/output (I/O) of acoustic information.Different mobile devices may include differing numbers and arrangementsof transducers, any of which may be suitable to facilitate acoustic I/O.

Mobile device 400 may also include one or more wireless communicationcomponents 460. For example, mobile communication devices such ascellular telephones will typically have a wireless transceiver capableof communicating with one or more cellular networks. Alternatively, orin addition to, wireless communication component 460 may include awireless transceiver capable of communicating with one or more othernetworks or external devices. For example, wireless communicationcomponent 460 may include a component configured to communication viathe IEEE 802.11 standard (Wi-Fi) to connect to a local area network(LAN), wide area network (WAN) such as the Internet, and/or may includea Bluetooth® transceiver to connect to a Bluetooth® compatible device.Wireless communication component 460 may also include a GlobalPositioning System (GPS) to communicate with a satellite network todetermine the location of the mobile device, or may include one or moreother wireless communication transceivers.

To simplify the illustration of exemplary mobile device 400, wirelesscommunication component 460 is used to represent any wirelesscommunication component 460 implemented on mobile device 400 and mayinclude one or multiple components that may be either separate orintegrated components, may be independent system components, or may bedifferent system components in communication with one or more otherwireless components. That is, wireless communication component 460denotes one or any combination of components that may be implemented ona mobile device that allows the mobile device 400 to communicatewirelessly with one or more networks, systems and/or other devices. Inthis manner, when mobile device 400 is active, mobile device 400 mayaccess automatic speech recognition services via one or more automaticspeech recognition servers connected to a network (e.g., automaticspeech recognition services provided via the cloud).

Mobile device 400 may also include a display 410 for visually presentinginformation to the user (e.g., presenting one or more prompts to theuser). Display 410 may also be configured as an input device, forexample, by responding to touch, pen input, etc. Mobile device 400 mayinclude one or more other input components 420 that allow a user tointerface with the mobile device. For example, button 420 may be used toinitiate wake-up of the mobile device when the mobile device has entereda low power mode such as a sleep mode and/or may be used as a selectionbutton or may include any other functionality when the mobile device isactive. Button 420 may be a power button, volume button, or any otherinput component having any desired functionality. Different mobiledevices may have different numbers and arrangements of input components420 depending on the design of the mobile device.

Mobile device 400 may also include other components such as one or morecameras 450, one or more light emitting diodes (LEDs) 470, one or moremotion detectors, and/or any other components. Mobile device 400 mayalso include a power port 490 for connecting the mobile device to apower source (e.g., wall power) and/or a data port forproviding/receiving data to/from another device connected via a datacable. According to some mobile device designs, the data and power portare the same port and can be used both for power and for data. It shouldbe appreciated that mobile device 400 is merely an example of a mobiledevice suitable for use with any one or combination of voice activationtechniques described herein. The mobile device components are describedto illustrate common features of smart phones, but no particular one orcombination of these components are required. Techniques describedherein are not limited for use with any particular mobile device havingany particular number or arrangement of components and any mobile devicehaving the ability to receive acoustic input may be suitable, as theaspects described herein are not limited in this respect.

FIG. 4B illustrates an example configuration of system componentsinternal to a mobile device, such as mobile device 400 illustrated inFIG. 4A. Exemplary system components of a mobile device may include aprimary processor 415, a secondary processor 425 and an audio codec 405,all illustrated for convenience and clarity of illustration as beinginterconnected via a common bus 455. Mobile device 400 also includes atleast one computer readable medium 435 for storing data, e.g.,instructions or programs that can be executed by the processors, statedata, or any other information utilized by the mobile device. It shouldbe appreciated that a given mobile device may include more or fewerprocessing components interconnected in any of numerous ways using anytype of interconnection, and the particular configuration illustrated inFIG. 4B is provided to demonstrate some concepts related to generallylow power functionality, in accordance with some embodiments.

It should be appreciated that any of the techniques described herein maybe implemented on a mobile device having a single processor (orperformed on a single processor even when multiple processors areavailable), and the following discussion with respect to FIG. 4B isprovided to describe an example of a mobile device configured to operatein one or more low power modes. As such, the configuration in FIG. 4B isused merely to illustrate a mobile device having a primary and secondaryprocessor that are capable of processing information and of exchanginginformation via some type of interconnection or series ofinterconnections or couplings and not to limit the type of mobile deviceon which techniques described herein may be implemented. In particular,mobile device illustrated in FIG. 4B is used to describe an example ofenabling and performing language independent wake-up word detection(i.e., wake-up word detection in a language for which an acoustic modelis generally not available in a current mode, such as a low power modeof a mobile device) to allow for voice activation and/or control in theuser's language.

Processor 415 may be the system's primary or main processor andgenerally operates as the central processing unit for the mobile deviceand, therefore may include a high speed processor that may consumerelatively large amounts of power when operating (e.g., when the clocktree is enabled and the processor is executing instructions).Accordingly, when a mobile device enters a low power mode (e.g., powersdown into a sleep or idle mode), the primary processor may be powereddown to a desired extent (e.g., one or more clocks in the clock tree maybe disabled to conserve power). When the mobile device wakes-up (e.g.,enters an active mode), the primary processor may be activated orpowered up to perform processing tasks that are needed. Generallyspeaking, when mobile device 400 enters an active mode, the device isenabled for network communications and can access cloud services (e.g.,automatic speech recognition services via the Internet).

Processor 425 may be a secondary processor such as a digital signalprocessor (DSP), co-processor and/or specialized processor to handlesome portion or aspect of the processing tasks performed by the mobiledevice, to assist the primary processor in performing certainfunctionality, to handle certain specialized processing tasks, and/or toperform certain processing tasks when mobile device 400 is operating ina low-power mode. As such, the secondary processor may be a lower powerprocessor than the primary processor in that less power may consumed bythe secondary processor when enabled and operating (e.g., executinginstructions). In some embodiments, the secondary processor can beconfigured to operate at a lower power and/or may be simpler and requireless power to power-up and/or keep enabled/powered-up, or may otherwisebe generally attractive from a power standpoint. In some embodiments,processor 425 is not a separate processor but instead is a part ofprocessor 415 that remains available in a low-power mode to performcertain processing tasks when mobile device 400 is in a sleep, idleand/or hibernate mode (e.g., in a low-power mode).

To allow for voice activation of a mobile device while operating in alow-power mode, the acoustic environment of the mobile device may needto be monitored in low power modes to obtain acoustic input anddetermine whether the acoustic input includes a wake-up word or whetherthe acoustic input resulted from spurious acoustic activity. The term“spurious acoustic activity” refers generally to any acoustic activity(including speech) detected in the acoustic environment of the mobiledevice that does not correspond to a wake-up word upon which the voiceresponse system can or should act. Thus, when mobile device 400 isoperating in a low-power mode, the mobile device 400 may not have accessto the network and/or it may not make sense from a power perspective toestablish a network connection each time acoustic input is received bythe mobile device 400 for evaluation as to whether a user has spoken awake-up word. As such, performing wake-up word detection may be limitedto the resources local to and/or resident on mobile device 400. In thisrespect, mobile device 400 may include local automatic speechrecognition resources (e.g., limited ASR resources) that include anacoustic model and a dictionary storing pronunciation information for asmall vocabulary of words, for example, one or more wake-up words, asmall command vocabulary, etc. The acoustic model may, for example, havebeen trained on training data predominantly or entirely in a sourcelanguage (e.g., English). The local automatic speech recognitionresources may be stored in computer readable medium 435 and deployed asone or more programs that can be executed by processor 415 and/orprocessor 425.

The user of mobile device 400 may speak a language different than thesource language on which the acoustic model was trained. To enablewake-up word detection in the language of the user, techniques describedherein may be performed. For example, method 200 described in connectionwith FIG. 2 may be performed to enable mobile device 400 to performwake-up detection in a target language different than the sourcelanguage on which the available acoustic model was trained. Inparticular, the user may be prompted to speak an enrollment utterancethat includes the desired wake-up word in the target language (e.g., thelanguage spoken by the user). The user may be prompted via mobiledevice, for example, using the display interface, via synthesized speechprovided via a speaker, or via any one or combination of interfaceelements. Mobile device 400 may obtain the enrollment utterance via oneor more microphones 130 provided on the device (e.g., by performingexemplary act 210 described in connection with FIG. 2 ). Mobile device400, either alone or using network resources, may process the enrollmentutterance by applying the wake-up word spoken by the user to theacoustic model (e.g., by performing exemplary act 220 described inconnection with FIG. 2 ). For example, acoustic features derived fromaudio of the user speaking the wake-up word in the target language maybe provided as input to the acoustic model trained in a source languageto obtain a sequence of speech units corresponding to the wake-up word.

The sequence of speech units obtained from the acoustic model may bestored in the dictionary on mobile device 400 (e.g., a dictionary storedon computer readable medium 435) as a reference sequence correspondingto the wake-up word spoken in the target language (e.g., by performingexemplary act 230 described in connection with FIG. 2 ). The storedsequence of speech units can thereafter be used as the referencesequence to perform wake-up word detection, as discussed above and infurther detail below. Additionally, the acoustic model local to mobiledevice 400 may be adapted to the user using the enrollment utterance andthe reference sequence of speech units (e.g., by performing exemplaryact 240 described in connection with FIG. 2 ) to improve wake-updetection for the particular user. Furthermore, the acoustic model maybe further adapted using one or more noise models to adapt the acousticmodel to one or more corresponding acoustic environments (e.g., byperforming exemplary act 250 described in connection with FIG. 2 ).

In this manner, an acoustic model available on a mobile device 400 (oravailable to a mobile device 400 in a low-power mode) can be used toenable wake-up word detection for one or more wake-up words in a targetlanguage spoken by the user. It should be appreciated that this processcan be repeated for any number of wake-up words. In particular, a usermay desire to have different wake-up words perform differentfunctionality. For example, a user may want to have a wake-up word forwaking the mobile device as well as a wake-up word to which the mobiledevice performs an associated task. Some tasks may require the mobiledevice to leave a low-power mode while others may not. Thus, byrepeating the process, a user can create a wake-up word commandvocabulary in the user's language using an available acoustic model onthe mobile device. Thus, language independent wake-up word detection maybe enabled to achieve voice activation and/or control in the user'slanguage.

Subsequent to enrollment, wake-up detection in the language spoken bythe user can be performed by mobile device 400. In particular, whenmobile device 400 is operating in a low power mode, the mobile devicemay monitor the acoustic environment to receive acoustic input (e.g., byperforming exemplary act 310 described in connection with FIG. 3 ). Forexample, in the low-power mode, microphone(s) 430 may continue toreceive acoustic input to which low level processing may be performed(e.g., voice activity detection, phone loops, spectral analysis, etc.).According to some embodiments, acoustic input received by microphone(s)430 is processed by an acoustic model local to the mobile device 400and/or available to the mobile device 400 in low-power mode to obtain asequence of speech units corresponding to the acoustic input (e.g., byperforming exemplary act 320 described in connection with FIG. 3 ). Forexample, acoustic features may be derived from the acoustic input andprovided as input to the local acoustic model to obtain an inputsequence of speech units characterizing the sounds of the acousticinput.

In turn, the input sequence of speech units may be compared to areference sequence of speech units stored on mobile device 400 (e.g.,stored on computer readable medium 435) to assess whether the user spokea wake-up word (e.g., by performing exemplary act 330 described inconnection with FIG. 3 ). As discussed above, any suitable comparisonmay be used to reach a determination as to whether the user spoke awake-up word in the target language. When it is determined that the userspoke a wake-up word, initiation of a transition from the low-powermode, initiation or performance of one or more tasks associated with thewake-up word, or a combination thereof may be performed (e.g., byperforming exemplary act 340 described in connection with FIG. 3 ). Asdiscussed above, the input sequence of speech units obtained from theacoustic input can be compared to any reference sequence stored on themobile device to determine if any valid wake-up was spoken by the user,and corresponding action may be performed when it is determined that thevalid wake-up word was spoken. In this manner, voice activation and/orcontrol of mobile device 400 in a user's language can be achieved evenif an acoustic model trained via the user's language may not beavailable to the mobile device 400 (e.g., when operated in a low powermode or otherwise).

An illustrative implementation of a computer system 500 that may be usedin connection with any of the embodiments of the disclosure providedherein is shown in FIG. 5 , for example, to implement any of thetechniques described herein. The computer system 500 may include one ormore processors 510 and one or more articles of manufacture thatcomprise non-transitory computer-readable storage media (e.g., memory520 and one or more non-volatile storage media 530). The processor 510may control writing data to and reading data from the memory 520 and thenon-volatile storage device 530 in any suitable manner, as the aspectsof the disclosure provided herein are not limited in this respect. Toperform any of the functionality described herein, the processor 510 mayexecute one or more processor-executable instructions stored in one ormore non-transitory computer-readable storage media (e.g., the memory520), which may serve as non-transitory computer-readable storage mediastoring processor-executable instructions for execution by the processor510.

To perform functionality and/or techniques described herein, theprocessor 510 may execute one or more instructions stored in one or morecomputer-readable storage media (e.g., the memory 520, storage media,etc.), which may serve as non-transitory computer-readable storage mediastoring instructions for execution by processor 510. Computer system 500may also include any other processor, controller or control unit neededto route data, perform computations, perform I/O functionality, etc. Forexample, computer system 500 may include any number and type of inputfunctionality to receive data and/or may include any number and type ofoutput functionality to provide data, and may include control apparatusto perform I/O functionality. For example, processor 415 and/orprocessor 425 and computer readable medium 435 may be implemented bycomputer system 500.

Processor 510 may execute any one or combination of programs that areavailable to the processor by being stored locally on computer system500 or accessible over a network. Any other software, programs orinstructions described herein may also be stored and executed bycomputer system 500. Computer system 500 may be the computer system on amobile device. Computer system 500 may also be implemented as astandalone computer, server, part of a distributed computing system, andmay be connected to a network and capable of accessing resources overthe network and/or communicate with one or more other computersconnected to the network (e.g., computer system 500 may be part of thenetwork resources available to a voice response system implemented on amobile device).

The terms “program” or “software” are used herein in a generic sense torefer to any type of computer code or set of processor-executableinstructions that can be employed to program a computer or otherprocessor to implement various aspects of embodiments as discussedabove. Additionally, it should be appreciated that according to oneaspect, one or more computer programs that when executed perform methodsof the disclosure provided herein need not reside on a single computeror processor, but may be distributed in a modular fashion amongdifferent computers or processors to implement various aspects of thedisclosure provided herein.

Processor-executable instructions may be in many forms, such as programmodules, executed by one or more computers or other devices. Generally,program modules include routines, programs, objects, components, datastructures, etc. that perform particular tasks or implement particularabstract data types. Typically, the functionality of the program modulesmay be combined or distributed as desired in various embodiments.

Also, data structures may be stored in one or more non-transitorycomputer-readable storage media in any suitable form. For simplicity ofillustration, data structures may be shown to have fields that arerelated through location in the data structure. Such relationships maylikewise be achieved by assigning storage for the fields with locationsin a non-transitory computer-readable medium that convey relationshipbetween the fields. However, any suitable mechanism may be used toestablish relationships among information in fields of a data structure,including through the use of pointers, tags or other mechanisms thatestablish relationships among data elements.

Also, various inventive concepts may be embodied as one or moreprocesses, of which examples have been provided. The acts performed aspart of each process may be ordered in any suitable way. Accordingly,embodiments may be constructed in which acts are performed in an orderdifferent than illustrated, which may include performing some actssimultaneously, even though shown as sequential acts in illustrativeembodiments.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, and/or ordinary meanings of thedefined terms.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e., “one or more” ofthe elements so conjoined. Other elements may optionally be presentother than the elements specifically identified by the “and/or” clause,whether related or unrelated to those elements specifically identified.Thus, as a non-limiting example, a reference to “A and/or B”, when usedin conjunction with open-ended language such as “comprising” can refer,in one embodiment, to A only (optionally including elements other thanB); in another embodiment, to B only (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

Use of ordinal terms such as “first,” “second,” “third,” etc., in theclaims to modify a claim element does not by itself connote anypriority, precedence, or order of one claim element over another or thetemporal order in which acts of a method are performed. Such terms areused merely as labels to distinguish one claim element having a certainname from another element having a same name (but for use of the ordinalterm).

The phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” “having,” “containing”, “involving”, andvariations thereof, is meant to encompass the items listed thereafterand additional items.

Having described several embodiments of the techniques described hereinin detail, various modifications, and improvements will readily occur tothose skilled in the art. Such modifications and improvements areintended to be within the spirit and scope of the disclosure.Accordingly, the foregoing description is by way of example only, and isnot intended as limiting. The techniques are limited only as defined bythe following claims and the equivalents thereto.

What is claimed is:
 1. A method of enabling wake-up word detection in atarget language on a user device, the method comprising: receivingacoustic input of a user speaking a wake-up word in the target languagewhen the user device is in a low-power mode; providing acoustic featuresderived from the acoustic input to an acoustic model stored on the userdevice to obtain a first sequence of speech units corresponding to thewake-up word spoken by the user in the target language, the acousticmodel trained on a corpus of training data in a source languagedifferent than the target language; comparing the first sequence ofspeech units with a reference sequence of speech units to recognize thewake-up word in the target language, wherein the reference sequence ofspeech units is obtained by applying acoustic features derived fromaudio comprising the user speaking the wake-up word in the targetlanguage to the acoustic model; responsive to recognizing the wake-upword, transitioning the user device from the low-power mode to an activemode; and adapting the acoustic model to the user using both thereference sequence of speech units and the first sequence of speechunits.
 2. The method of claim 1, further comprising adapting theacoustic model to the user using the acoustic input of the user speakingthe wake-up word in the target language and the sequence of speech unitsobtained therefrom via the acoustic model.
 3. The method of claim 1,wherein the sequence of speech unit comprises a phoneme sequencecorresponding to the wake-up word spoken by the user in the targetlanguage.
 4. The method of claim 1, further comprising associating atleast one task with the wake-up word to be performed when it isdetermined that the user has spoken the wake-up word.
 5. A user deviceconfigured to enable wake-up word detection in a target language, theuser device comprising: at least one microphone configured to obtainacoustic information from an environment of the user device; at leastone computer readable medium storing an acoustic model trained on acorpus of training data in a source language different than the targetlanguage; and at least one processor coupled to the at least onecomputer readable medium and programmed to perform: receiving, from theat least one microphone, acoustic input from the user speaking a wake-upword in the target language when the user device is in a low-power mode;providing acoustic features derived from the acoustic input to theacoustic model to obtain a sequence of speech units corresponding to thewake-up word spoken by the user in the target language; comparing thesequence of speech units to a reference sequence of speech units,wherein the reference sequence of speech units obtained by applyingacoustic features derived from audio comprising the user speaking thewake-up word in the target language to the acoustic model; and adaptingthe acoustic model to the user using the sequence of speech units andthe reference sequence of the speech units.
 6. The user device of claim5, further comprising adapting the acoustic model to the user using theacoustic input of the user speaking the wake-up word in the targetlanguage and the sequence of speech units obtained therefrom via theacoustic model.
 7. The user device of claim 5, wherein the sequence ofspeech units comprises a phoneme sequence corresponding to the wake-upword spoken by the user in the target language.
 8. The user device ofclaim 5, further comprising associating at least one task with thewake-up word to be performed when it is determined that the user hasspoken the wake-up word in the target language.
 9. A method ofperforming wake-up word detection on a user device, the methodcomprising: while the user device is operating in a low-power mode:receiving acoustic input from a user speaking in a target language;providing acoustic features derived from the acoustic input to anacoustic model stored on the user device to obtain a first sequence ofspeech units corresponding to the acoustic input, the acoustic modeltrained on a corpus of training data in a source language different thanthe target language; determining if the user spoke the wake-up word atleast in part by comparing the first sequence of speech units to areference sequence of speech units stored on the user device, whereinthe reference sequence of speech units obtained by applying acousticfeatures derived from audio comprising the user speaking the wake-upword in the target language to the acoustic model; exiting the low-powermode if it is determined that the user spoke the wake-up word; andadapting the acoustic model to the user using both the referencesequence of speech units and the first sequence of speech units.
 10. Themethod of claim 9, wherein the acoustic model was adapted to the userusing the audio comprising the user speaking the wake-up word in thetarget language and the reference sequence of speech units obtainedtherefrom via the acoustic model.
 11. The method of claim 9, furthercomprising performing at least one task associated with the wake-up wordif it is determined that the user spoke the wake-up word.
 12. The methodof claim 9, wherein the first sequence of speech units comprises aphoneme sequence corresponding to the acoustic input, and wherein thereference sequence of speech units comprises a phoneme sequencecorresponding to the user speaking the wake-up word in the targetlanguage.
 13. The method of claim 9, wherein exiting the low-power modecomprises transitioning the user device from an idle mode to an activemode.